Blade system of gas or steam turbines



Sept. 30, 1930. A. LLLLL LM A 1,777,098

Patented Sept. 30, 1930 :UNlTED STATES PATENT OFFICE ALF LYSHOLM, OF STOCKHOLM, SWEDEN, ASSIGNOR TO AKTIEBOLAGET LJUNGSTROMS ANGTURBIN, OF STOCKHOLM, SWEDEN, A JOINT-STOCK COMPANY BLADE SYSTEM OF GAS'OR STEAM TURBINES l Application filed June 21, 1928, Se'al No. 287,176, and in Sweden Tune 30, 1927.

the total number of blades required in a turbine.

A characteristic combination of features of the invention is that the thickness of each blade is greater at the inlet side of the blade than at the outlet side thereof, and that the blade pitch is related to the height of the blades as la: 'JSII oc, where 72 :0.5 and 1.-5 and o designates the outlet angle of the blade.

A further characteristic combination of features according to the invention is that the maxinum thickness of each blade is on the inlet sideof the line of gravity of the blade and thence decreases toward the outlet side, and that the blade pitch is relatedto the height of the blades as la: J sin a, where k 0.*5 and 1.5 and a designates the outlet angle of the blade.

A further characteristic combination of features is that each blade has a rounded shape toward the incoming steam, and thatthe blade pitch isrelated to the height of the blades as k/sin a, where 70:05 and 1.5. and (x designates the outlet angle of the blade.

A further characteristic combination of features is that the thickness of each blade is greater at the inlet side of the blade than at the outlet side thereof` and that the blade pitch is 0.9 to 1.5 times the dimension of the blades, measured in the direction of flow of the driving fluid.

A further characteristic combination of features is that the maximum thickness of each blade is on the inlet side of the line of gravity of the blade and thence decreases toward the outlet side, and that the blade pitch is 0.9 to 1.5 times the dimension of the blades, measured in the direction of flow of the driving fluid.

A further charactertistic combinaton of features is `that each blade has a rounded 'shape toward the incoming driving fluid, and that the blade pitch is 0.9 to 1.5 times the dimension of the blades, measured in the direction of flow of the driving fluid.

The feature of. providing rounded inlet edges in the blades of elastic fluid turbines, and of thus imparting to the blades a streamline contour to increase the eificiency of the individual blades, is known to be previously suggested in the art of turbine design, whereas the Combined features of rounding the inlet edges of the blades or of locating the maximum thickness of each individual blade to the inlet side of the blade, and of providing a blade pitch which is related t`o the height of the blades as 73: sin a, where la 0.5 and 1.5 and oz designates the outlet angle of the blade, or which is 0.9 to 1.5 times the height of the blades, are novel and characteristic of my present invention, to the best of my knowledge and belief.

In the accompanying drawings, Fig. 1 represents a cross-section of one of the blades of the improved blade system according to the invention. Figs. 2 and 3 show a few blades of the type considered in connection with the present invention and spaced as they Will be in a blade system according to the invention.

'With reference to Fig. 1 of the drawings, A denotes the center of gravity of the blade, While B is the center line of the blade. This center line is divided into three equal parts, and through the dividing points intersecting lines C and D are drawn at right angles to the center line. E is the height of the blade, that is to say, its dimension measured in the direction of flow of the driving fluid, this direction being an axial one in an aXial-flow turbine and a radial one in a radial-flow turbine. oc designates the outlet angle of the blade.

As will be clearly seen, the greatest. thickness of the blade is on the inlet side of the blade, the said thickness being located in front of the center of gravity A. The mass of the blade is so distributed with respect to the outlet angle oz that the most suitable blade pitch of the turbine, that is to say, the most measured in the direction of flow of the fiuid, the same being between the limits 0.9 to 1.5 times the said dimension, whereas in the blade Systems as hitherto devised the blade pitch is only about 0.7 times the dimens'ion of the blade, measured in the direction of flow of the fiuid. Consequently, the advantage is gained through the present invention that a smaller number of blades are required in the whole turbine than hitherto, the possible rei duction of' the number of blades being, in

` account of the increasing Width and roundoutlet side,

.rected toward the entering steam is rounded ing of the blade section toward the incoming steam, eddies which arise in previously known blade systems on account of' varia tions in the direction and Velocity of the incoming steam jet are not produced. It has been shown by trials that the incoming steam may vary materially both with respect to velocity and direction, without the eiliciency of the blade system being appreciably impaired thereby.

As illustrated, the blades of a blade system according to the invention are given a greater thickness at the inlet side than at the and the edge of the blade dion the lines of a circle, ellipse parabola or hyperbola, or has an approximately Similar shape.

By thus adopting blades of the shape disclosed in Figs. 1, 2 and 3 for the blade system according to the present invention, the further advantage is gained, in addition to that of a reduced blade pitch, that the losses will be comparatively ind'ependent of the direction of the incoming steam jet. Therefore, the efliciency of the blade system will be independent of the variations and speed conditions involved by overloading, reduced loading or a variable number of revolutions of the turbine. Moreover, when steam is used as a driving fiuid, such blade Systems are suitable in localities where the percentage of moisture of the steam is high, inasmuch as they offer, in the first place, greater resistance to wear and, furthermore, are suited to the altered inlet angles under which the moisture of the steam is supplied to the blade system.

Inasmuch as the novel blade systems are to a greater extent independent of the inlet angle of the fluid, it is no longer necessary, as

is the case in certain turbines, that blades are made in difierent Sizes, for instance with a radial dimension of 5, 7 and 10 millimeters, and that each dimension is made in 10 difierent blade nrofiles suited to different inlet and outlet angles, or, altogether, about 30 different blade profiles. Blade systems according to the invention may be built with blades of a single size having a dimension of 10 millimeters'in the direction of flow of the fiuid, and only 2 or 3 blade profiles are required for different directions and Velocities of the fiuid. In the standardization of turbine manufacture with blade Systems according to the invention it will thus only be necessary to make of the number of blade types that has been previously required.

On account of the above it may be of advantage, economically, to provide blades milled in their entirety and inserted directlv into the ring bonds uniting the blades in the blade rings, it being then also possible to make the outer blade lengths at least 20% longer, whereby the output of the turbine may be increased in a. corresponding degree, if the same blade length is employed, while the height of the blade is reduced, the sum of the squares of the speeds may be increased. In order to obtain a turbine, for eX-, ample a back pressure turbine with possibilities of overloading by means of by passage while maintaining a good efiiciency under all conditions, the relation of veloci y should be great. With a blade system according to the invention this relation g may be increased to values 0.8, without the thin blades of earlier constructions being obtained. Moreover, a turbine constructed with a blade system according to the invention will obtain an increased turning moment at the moment of starting, and for this reason such a turbine can better be used, for instance as a motor for the driving of locomotives, whereby the capability of the locomotive to force gradients is increased.

What .I claim as new and desire to secure by Letters Patent of the United States of America is:-

1. In a blade system for gas or steam turbines, the combination of the features that the thickness of each blade is greater at the inlet side of the blade than at the outlet side thereof, and that the blade pitch is related to the height of the blades as lea/sin oz, where la: 0.5 and 1.5 and x designates the outlet angle of the blade.

2. In a blade system for gas or steam turbines, the combination of the features that the maximum thickness of each blade is on the inlet side of the line of gravity of the blade and thence decreases toward the outlet side, and that the blade pitch is related to the height of the blades as lea/sin a, where mwanae lt: 0.5 and (1.5 and oc designates the outlet angie of the htade.

3. In a blade system for gas er stean turhines, the combination of the features that each blade has a rounded shape toward the incoming steam, and that the blade pitch is related to the height of the blades as 16: sin 0:

Where ic 0.5 and 1.5 and oc designates the i outlet angle of the hlade.

4. In a blade system for' gas'or steam turhines, the combination of .the features'that the thickness of each blade is greater at the inlet side of the hlade than at the outlet side thereof, and that the blade pitch is 0.9 to 1.2 times the height of the blades.

5. In a blade system for gas or steam turhines, the combination of the features that the maximum thickness of each blade is on the inlet side of the line of gravity of the blade and thencedecreases toward the outlet side, and that the hlade pitch is 0.9 'to 1.2

times the height of the Tolades. l

6. In a blade system for gas or stearn turhines, the combination of the features that each biade has a rounded shape toward the incoming driving fluid, and that the blade pitch is 0.9 to 1.2`tiines the height of the hlades.

7. In a hiade system for gas or steam turhines,-the combination of the features that the inlet edge of each blade is of a circular cross-section, and that the' bladepitch is related to the height of the blades as ita/sin az, Where is: 0.5 and 1.5 and a designates the outlet angle of the blade. v

8. In a blade system for gas or stean'turhines, the .comhination of the features that the inlet edge of each blade is of a circular cross-section and that the hlade pitch is 0.9 to 1.2 times the height of the blades.

9. In a hlade system for gas or steam turbines, the combination of the features that the maximum thickness of each hlade is on V the iniet side of the `line of gravity of the hlade and thence decreases toward the outlet side, and that the blade pitch is .9 and 1.5 times the height of the hlades.

In testimony whereof Iax my signature.

ALF LYSHOLM. 

